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  <meta charset="UTF-8">
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  <title>Document</title>
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<body>
  
</body>
<script>
  var arr = [1,2,3,4,5,3,4,6,8,1];
  Array.prototype.myFun = function() {
    var newArr = [];
    for(var i=0;i<arr.length;i++){
      var result = newArr.indexOf(arr[i]);
      if(result == -1) {
        newArr[newArr.length] = arr[i]
      }
    }
    return newArr
  }
  console.log(arr.myFun());
</script>
</html>